General Methods: Melting points were uncorrected and measured on an XT-4 apparatus. IR spectra were recorded from KBr pellets at a range of 400-4000 cm -1 on a Thermo Nicolet Nexus 470 FTIR spectrometer. 1 H and 13 C NMR spectra were obtained on a Varian Mercury VX300 apparatus or a Bruker DPX400 apparatus in CDCl 3 , D 2 O or DMSO-d 6 with TMS as internal standard. The elemental analysis (C, H, and N) data were obtained from a VarioEL III (German) elemental analyzer. Single-crystal

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... ction measurements were carried out on a Bruker Smart-APEX-CCD diffractometer. Column chromatography was performed using EM silica gel 60 (230-400 mesh). Thin-layer chromatography (TLC) was performed on glass plates precoated with silica gel (5-40 μm) to monitor the reactions. Visualization was accomplished by spraying chromatograms with a solution of sulfuric acid-ethanol (1:10, v/v) and heating in an oven at 105°C for 3 min until color developed. Materials: All solvents were purified according to reported procedures. Unless otherwise noted, reagents and materials were obtained from commercial suppliers and were used without further purification. Single Crystal Structure Determination: Single-crystal X-ray diffraction measurements for the four compounds (3a, 3e, 5e and 2α-(1H-pyrazol-1-yl)-5α-androstan-3,17-dione) were carried out on a Bruker Smart APEX CCD-based diffractometer equipped with a graphite crystal monochromator for data collection. The determinations of unit cell parameters and data collections were performed with MoK α radiation (λ = 0.71073 Å), and unit cell dimensions were obtained with least-squares refinements. The program Bruke SAINT7 was used for reduction date. All structures were solved by direct methods using SHELXS-97 (Sheldrick, 1990) and refined with SHELXL-97 (Sheldrick, 1997); 1 non-hydrogen atoms were located in successive difference Fourier syntheses. The final refinement was performed by full matrix least-squares methods with anisotropic thermal parameters for non-hydrogen atoms on F 2 . The hydrogen atoms were treated by a mixture of independent and constrained refinement. The absolute configurations of the starting materials are known and certain stereocentres (including the carbon atoms with an angle methyl) do not change, then the absolute structure of products can be inferred. Therefore, the results of the Flack parameter fields are meaningless. The ORTEPs of the four compounds are showed at the 30% probability level. Supplementary Material (ESI)